Mechanical Ventilation Flashcards by Shawn McGurran

What type of trigger variable may be more responsive to a patient breathing pattern

Flow triggered

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What is the advantage and disadvantages of the volume cycled variable in mechanical ventilation?

Advantage: minute volume will remain constant to provide stable blood gases

Disadvantage: as lung compliance or resistance, worsen, PIP, and plateau pressure increase, which may cause barotrauma, or volutrauma.

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What is the normal cycling variable in pressure support ventilation?

Flow cycling

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What are the alarm settings for high-pressure, minimum exhaled volume, XL, low pressure, and oxygen in mechanical ventilation

-High pressure set 10 cm H2O above peak airway pressure
-Minimum exhaled volume set 100 mL below exhaled tidal volume.
-Low pressure set 10 cm below peak airway pressure
-Oxygen set 5% above and below FiO2 setting

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What 3 devices, verify accuracy for volume, pressure, and flow

Volume-barometer,

Pressure-mercury or water manometer

Flow-Rotamater

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What are the indications for continuous, mechanical ventilation?

Apnea
Acute ventilatory failure
Impending ventilatory failure -trend of rising, PCO2 and or decreasing Vt, Vc and MIP
Oxygenation

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What bedside ventilator parameters can indicate mechanical ventilation is necessary

Vital capacity < 10 mL/kg
MIP <20 cm H2O
RR <8 or >20
Tidal volume < 5 mL/kg
VE >10 L/min

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What physiological assessment or calculations indicate mechanical ventilation is necessary

Deadspace greater than 60%
Shunt greater than 20%
Static compliance < 25 mL/cn H2O
A-a DO2 >300 torr

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What are the initial settings for mechanical ventilation?

Vt= 5-10 mL/kg of ideal body weight
Pressure (PC)= use plateau from VC or <35 cm H2O
RR=10-20
FiO2=40-60, set at lvl prior to ventilation
PEEP=2-6.. set at lvl prior to ventilation

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What is the formula to determine ideal bodyweight weight?

50 kg + (2 x inches over/under 5 ft.

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Increasing what ventilator parameter best increases alveolar ventilation

Tidal volume

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How much dead space is in an inch of flex tubing

10 mL

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The sum of anatomic and alveolar deadspace is called what

Physiologic deadspace

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What is the frictional force that must be overcome during breathing called and what is the normal range?

Airway resistance

0.6-2.4 cm H2O/L/sec. As high as 6 in intubated patients

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What are two common causes and treatments for increased peak pressures?

Secretions in airway – suction

Broncospasm – broncodilators

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What are the causes and suggested treatments of decreasing lung compliance (Cl)?

-Atelectasis
-Pulmonary edema
-ARDS
-Pneumonia

Increase PEEP and treat underlying cause

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What ventilator control has the greatest influence on mean airway pressure (Paw)?

PEEP

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What is the typical mean airway pressure in obstructive disease?

10-20 cm H2O

Normal: 5-10
ARDS: 15-30

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Mean airway pressure (PAW) has the greatest impact on what life function

Oxygenation

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How can you measure the work of breathing?

Change and pressure multiplied by the change in volume

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What happens when work of breathing increases and respiratory muscles tire

Tidal volume decreases and respiratory rate increases

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What are indications to switch a patient to SIMV

-Tachypneic patients to avoid hyperventilation
-To lower mean airway pressures.
-Used with peep to reduce barotrauma

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Inverse ratio ventilation (IRV) improves, oxygenation and gas exchange and decreases PIP and PEEP levels. What patient criteria would indicate its use?

-patients requiring FiO2 over 60% and peeps greater than 15 cm H2O.
-PIP’s greater than 50 cm H2O
-Low PaO2 with decreased compliance

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What ventilation mode is a form of spontaneous breathing at a positive pressure level, similar to CPAP, That occasionally releases the baseline pressure resulting in lower PIPs and mean airway pressure?

Airway pressure release ventilation (APRV)

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What ventilator mode improves oxygenation using lower mean airway pressures

Airway pressure release ventilation (APRV)

What ventilator mode is a form of ventilation that keeps pressure at the lowest level by providing automatic breath to breath, pressure regulation while providing a preset volume

Pressure regulated volume control (PRVC)

What mode of ventilation has the characteristics or where pressure, volume and flow are proportional to the patient’s spontaneous efforts

Proportional assist, ventilation (PAV, or PAV+)

How would you initially determine settings for pressure support ventilation?

By calculating the patient’s airway resistance (PIP-Plateau).

What is the goal of pressure support ventilation

Overcome the resistance of the ventilator circuit and endotracheal tube during spontaneous ventilation

What mode of ventilation is indicated with PIP’s > 50 cm H2O or air leak syndromes to improve oxygenation Impatience with severe lung injury

High frequency oscillatory ventilation (HFOV)

What are the typical Hertz settings in high frequency oscillatory ventilation (HFOV)

3 to 15 Hz 1 Hz equals 60 cycles per minute 5 Hz equals 300 breaths per minute

In high frequency oscillatory ventilation, HFOV, what is the characteristics and goals of the ventilator parameters?

Very high, respiratory rates result in low alveolar pressure changes Title volumes are very low (< 5 mL)

What are the two ways you would decrease PaCO2 in HFOV?

Primary-increase amplitude Secondary-Decrease Hz frequency

When you wish to normalize a high PCO2 during mechanical violation, you should follow what order of?

1. remove mechanical, dead space if possible 2. Increase the tidal volume or PIP 3. Increase the respiratory rate.

When you wish to normalize a low PaCO2, you should follow what order of steps

1. evaluate the cause (hypoxemia, pain, fever and anxiety) 2. decrease the respiratory rate 3. Decrease the tidal volume or PIP.

When you wish to increase a low PaO2, you should follow what order of steps

1. Increase FiO2 by 5 to 10% up to 60%. 2. increase peep levels by 2 to 5 cm H2O until acceptable oxygenation achieved or unacceptable side effects occur

What are potential side effects of high levels of peep?

Decrease compliance Decreased cardiac function Barotrauma Increased C(a-v)O2

What is the order of steps to decrease a high PO2?

1. Decrease to less than .60 2. Decrease PEEP

What are the ARDS net protocols?

1.Initial title of 8 mL/kg IBW and then reduce to 6 mL 2. Maintain plateau pressures < 30 cm of H2O 3. Consider permissive hypercapnia and subsequent respiratory acidosis.

What is the goal of a recruitment maneuver (RM)?

Sustained increase in pressures in along with the goal of opening as many collapsed lung units as possible

Please describe the most common recruitment maneuver (RM) for both peep and CPAP

Peep: increase peep to 40 cm of H2O for 40 seconds CPAP: increase CPAP levels to 20 cm H2O for 20 seconds

If SPO2 rises and then falls, how many times can you consider repeating a recruitment maneuver?

Once

When should prone positioning be considered?

When FiO2 levels > .60 and PEEP levels are greater than 12 cm of H2O or when recruitment maneuvers have failed

Proning is successful in what percent of patient patients with ARDS and should improve PO2 within 30 minutes

75%

When successful, prone positioning, has what impact on PaO2, PaCO2, and shunt?

PaO2-increase by 10 to 50 torr PaCO2-May decrease Shunt-decreased by 12 to 25%

In normal loop graphics, what characteristic identifies an assisted breath?

A fish tail

What are high and low inflection points used for?

High – best volume Low – best peep

What type of loop best identifies airway resistance, and what shape is characteristic of high airway resistance

A flow volume loop Flattened ball

What does a broken loop in a ventilator graphic indicate?

An air leak

How can you identify water condensation in a flow volume loop?

Scalloped pattern

What type of ventilator graphic helps determine best peep, and volume?

A volume Pressure loop

What type of graphic is used to identify auto peep and how?

Scalar graphics. The expiratory flow does not return to baseline before the next breath starts.

What are adverse effects of auto peep?

-Decreased cardiac output. -Decreased blood pressure -Increased intracranial pressure -Over distention of alveoli resulting in barotrauma -Difficulty triggering the ventilator

What are some reasons for an auto trigger in mechanical ventilation?

-Bounding pulse or cardiac movement -Leaks in circuit or airway. -Inappropriate trigger setting -Condensation in circuit

What type of medication is used to decrease anxiety and promote relaxation and what are some names?

Sedatives, the ams and pams Diazepam

What type of medication can reduce a patient’s ability to perceive sensation and what are some drug names?

Anesthetic Propofol ketamine Etomidate

What type of medication reduces a patient sensation of Pain and what are a few common drugs

Analgesics & opioids Morphine Codeine Fentanyl Oxycodone, and all other dones

What are neuromuscular blocking agents used for?

Cause paralysis of skeletal muscle Pancuronium and all onium meds

What is the best method to evaluate if a patient is ready for weaning

A spontaneous breathing trial with CPAP and with or without pressure support

What is the minimum and maximum time for a spontaneous breathing trial?

30 minutes up to 2 hours

What is the heart rate and respiratory rate criteria for termination of a spontaneous breathing trial. What are some other indicators?

Respiratory rate > 35 BPM for over five minutes Heart rate greater than 130 or 20% over baseline Blood pressure instability, Systolic blood pressure greater than 180 or less than 90 Cardiac arrhythmias Oxygen saturation less than 90% or decreased 4% from baseline pH less than 7.30

How long should you wait to repeat a spontaneous breathing trial (SBT)?

24 hours

What types of drugs should be discontinued for a SBT?

Narcotics neuromuscular blocking agents Anesthetics

How long after a ventilator wean has been initiated should an ABG be run?

20-30 minutes

Atelectasis can be common following extubation. What should be recommended to prevent it?

SMI or IPPB

After how long of failed weaning attempts is a patient considered ventilator dependent

Three months

What are the indications for noninvasive positive pressure ventilation

Acute exacerbation of chronic respiratory failure (COPD) Congestive heart failure or pulmonary edema. Severe dyspnea with a do not intubate order

What are the advantages of NPPV?

Avoids ventilator associated pneumonia Avoids complications of an artificial airway Avoids complications of mechanical ventilation

What are the recommended initial settings for NPPV?

IPAP: 8 to 12 cm H2O EPAP: 4 to 6 cm of H2O

How do you calculate rapid shallow breathing index and what’s acceptable

RR / VT in L (ie. 0.4) Less than 100